This man was tasked with putting a price tag on Ground Zero real estate

The One World Trade Center building is reflected on one of the pools at the 9/11 Memorial in New York. AP Photo/Richard Drew

The aftermath of the September 11 terrorist attacks in 2001 was a tragic time for America. As the nation mourned, the question eventually turned to the matter of the targeted areas. What would happen to the World Trade Center site? The Pentagon? The area where United Airlines Flight 93 landed?

Before anything could be developed there — any memorial or museum — those sites needed to be appraised for their real estate value. How much is the land under the former Twin Towers worth?

Randall Bell, head of Landmark Research group, was hired to appraise the World Trade Center and Flight 93 sites. He's an innovator in the field of appraisals, having invented the Bell Chart in 1993, a complicated matrix that accounts for hundreds of different factors to determine the value of a location.

Throughout his career, Bell has analyzed dozens of stigmatized properties — everything from Nicole Brown Simpson's condo, to the mansion where Heaven's Gate members committed mass suicide, to houses thought to be haunted.

The 9/11 attack sites produced a unique set of challenges. The values of the New York and Flight 93 sites were affected in different ways.

"In New York, those two towers were worth enormous amounts of money, and when they were destroyed, the values obviously went down considerably," Bell told Insider. "With the Pennsylvania site, the Flight 93 crash site, it was the opposite. The land there originally wasn't worth a lot, but the value actually went up considerably."

The reason, Bell says, has to do with the economics of memorials. There's a free component to memorials, where people pay their respects, and then there's also a component that generates revenue, where souvenirs and books are sold.

"A lot of people might be surprised to think about it this way, but memorials generate an income," Bell said. "With that level of income, it was much lower than what was in New York in terms of [the] financials of it. But with Pennsylvania, that actually increased the value."

To appraise the World Trade Center site, Bell was hired by the Lower Manhattan Development Corporation, the entity that owns the land there.

The site was divided into four quadrants. Bell was assigned to the site of "the footprints," as he calls them, of the Twin Towers. There would eventually be the memorial there. Other people focused on the areas where new towers would be built.

"There's a lot of emotion," Bell said. "Like any American, I was pretty shocked. But then there's also the practical issues you've got to address and keep moving forward."

The LMDC assigned Bell to conduct a "Highest and Best Use Analysis," to determine what kind of memorial should be built there. To do that, he traveled all over the world to do research on comparable sites, including Hiroshima, Pearl Harbor, and Oklahoma City.

He also went to Graceland, where Elvis Presley was buried, because he said they have a memorial there that's similar to the reflecting pool that was built at the World Trade Center site.

What Bell recommended in his final report became exactly what was built at the World Trade Center: the reflecting pool as the free component, but a museum that charges attendees.

"The World Trade Center site was larger and more complicated than a lot of people realize," Bell said. "Rudy Giuliani — who I happen to think is a good guy — he wanted to turn it all into a memorial. And I thought, 'Well, on a practical basis, you can't do that.'"

The crash site of United Flight 93 at the Wall of Names in Pennsylvania. AP Photo/Gene J. Puskar

The site of the Flight 93 crash was on private property, and Bell said the owner didn't know what to do with it. A year after the attack, Congress passed a law for the National Park Service to build a memorial there.

The owner enlisted Bell in a legal battle with the government over the land's value. The government wanted to pay the owner for his land, but said that its value was no different from anywhere else in rural Pennsylvania. Bell argued that the value of a place is modified by historical events that take place there.

"You take a Revolutionary War site," Bell said. "They're just open fields. But they're very historically significant. And when you add book stores, museums, and so forth, they all generate significant income."

Bell won the case. In his opinion, though, the National Park Service didn't end up building the ideal memorial. He recalls the wreckage of the site when he first went there, the twisted metal of the plane among nearby trees and cabins.

"It was a pretty grim site," he said. "If you go there, you can't see what it looked like originally, which I think is unfortunate. I think it would have been more appropriate to preserve the site as it originally was. And that wasn't done."

Following 9/11, Bell had to appraise several other related, stigmatized properties. With intelligence gathered after the attacks, the FBI identified sites that were targets for other attacks. The specifics are confidential, Bell said, but his résumé says that he "calculated the damages, if any, caused to a large landmark property in the Southern California area which had been identified by the FBI as a specific terrorist target in the aftermath of the attacks of September 11, 2001."

"That was a little sobering, because I grew up my whole life in Orange County," Bell said. "To realize that terrorists were actually targeting properties and sites in Orange County — and I'm not just picking on Orange County, it's around the country — it brought that issue to home. It's a serious problem that really kind of affected everyone."